Movable iron instrument



Jan. 2, 1951 A. E. ANDERSSQN MOVABLE IRON INSTRUMENT 2 Sheets-Sheet 1 Filed April 16, 1945 Iii/v ale/tor i .fimelsson Jan. 2, 1951 A. E. ANDERSSON 2,536,526

MOVABLE IRON INSTRUMENT m" III III llllll l I I iliillllllllllllllllllllIII|IllIllllllllllllllllllllllllll Patented Jan. 2, 1951 UNITED STATES PATENT OFFICE MOVABLE IRON INSTRUMENT Albert Emanuel Andersson, Flysta, Spanga; Swe- I den, assignor to Telefonaktiebolaget L M Erics- I son, Stockholm, Sweden, a company of Sweden Application April 16, 1945, Serial No. 588,484

In Sweden May 13, 1944 .2 Claims (01. 171-95) The invention relates to a movable. iron instrument in which an iron core, carried by a rotatable shaft cooperates with a stationary iron core in such a manner that both repel each other upon excitation of a coil enclosing them. It is a very tedious work to adjust such an instrument after manufacturing, especially when previously marked scales are to be used. If for instance the spring of a certain instrument has too great a torque so that the deflection does not attain the desired value for a certain current through the coil, one "has hitherto been compelled to detach the spring and reduce the torque to the marked scale as soon as an adjustment of the instrument, performed by means of a displacement of the stationary iron, is made. The scale distribution is in other words not invariable by adjustment but variable. I

It is an object ofthe present invention to provide an instrument enabling an adjustment of the instrument without the scale distribution thereby being changed, should even rather great variations in spring torque or magnetization appear.

The invention will be described in detail with reference to the enclosed drawings showing two embodiments. Fig. 1 is a partial cross section through an instrument according to the invention and Fig. 2 shows the radial and the circumierential portions of the iron. Fig. 3 shows the stationary iron and a sleeve carrying it.

Fig. 4 shows in partial cross section a modification of the invention, by which the instrument is provided with an additional stationary repulsion iron and Fig. 5 shows in plan the stationary irons for said instrument. Figs. 6 and '7 show the two sleeves and the irons fixed thereon.

In Figs. 1 to 3, I is the coil winding, 2 the pointer of the instrument, 3 the movable, radially disposed iron mounted on the shaft carrying the pointer. The stationary iron consists of two parts 4 and 5 constituting a unit, part 4 of which being radially disposed and part 5 extending circumferentially along the inner cylindrical surface of the coil. The iron 4 is made together with iron 5 out of one piece of iron sheet,

positions in the. hole of the coil.

z I a the iron part 4 thereby being bent at right angles to the iron 5. Fig. 2'shows the shape of the two irons, the breadth of iron 5 first sharply decreasing along a curved line A (Fig. 2) in the deflection direction, and thereafter more slowly decreasing along a straight line B. The irons 4 and 5 are carried by' a cylindrical iron sleeve 6 of non-magnetizable material (Fig. 3) which by means of the strip 1 may be displaced to difi'erent If now the springiof a certain instrument has toogreat a moment, a certain current does not give a dc:- flection sufficient to move. the pointer to the proper position on the-scale and the iron 4--- 5 in the scale-distribution, that would arise by a displacementv of the radially disposed iron. part 4 alone, and which is due to the repulsing force between irons 3 and 4 decreasing with the square of the distance between irons 3 and 4 will be avoided if the iron 5 is connected to the iron-4 and consequently displaced at the same time as the iron 4 is displaced (in clockwise direction in Fig. 1), so that the iron 5 after displacement of irons 4-5for the same current intensity will occupy another position in relation to the iron 3, the latter thereby being influenced by the iron 5 with another force than before. By dimensioning and shaping of the iron 5 as above described it is now possible to attain that the sum of the forces, by means of which the iron 3 in each position of same is influenced by the radially disposed iron 4 and the clrcumferentially disposed iron 5, has such a magnitude that the scale distribution will be unchanged even after an adjust ment of the instrument by means of displacement of the combined iron 4.5. If for instance the printed scale is linear there is proportionality between current increase .(from an arbitrary value of the current force) and corresponding increase in the deflection and this proportionality is maintained also after an adjustment of the instrument through displacement of the irons 4.5. If instead the spring of the instrument should have too small a moment so that acertain current gives too great a deflection the two irons 4' 5 are to be turned in counterclockwise direction (Fig. 1), the distance between the two irons 3 thereby being increased until the deflec;

ec'reases sufficiently to bring the pointer to 3 the proper position on the scale. It is evident that the desired effect depends on the form of the iron 5 as well as on the thickness of the same, the proper shaping for a certain material thereby being achieved empirically. The form of the iron 5 shown in Fig. 2, wherein the outer edges are curved in the vicinity of the iron 4, has proved to be suitable for an iron thickness of about 0.3 mm.

It has proved to be possible to adjust an instrument according to the invention if the moment of the spring is up to too strong'or too weak, the instrument thereby" showing right. in each position of the scale with an accuracy of i0.5% and the scale-distribution thus being inainly unchanged.

Figs. 4-6 ShOW an embodiment showing' the as radially disposed iron 4-6 when the latter apt proaches its end position, thelast portion. of: the scale thereby being strongly crowded. ,"Io prewe'ntthis crowded portion from extending over. a long portion of the scale the sleeve llalso carries a trapezoidal additional iron 15, the device being shaped'in such a waythat the iron and the circumferential part of the. iron 13 over-lap each other more or. less according, to the position of the sleeves II and 12. (as is shown'in Figs. '4 ands-7). I

Th invention is: not. limited/to the embodiments described but'can be modified in several waysfilclaimz IDA movable iron instrument comprising a scale, an ironv core. part carried. by a rotatable shaft and arranged to cooperate with, a stationary iron. core, and a current-conductingv solenoid enclosing said iron core part and said stationary iron core, said stationary iron core comprising a radially disposed portion and a circumferentially disposed portion, the latter portion extending along the inner surface of said solenoid and having its breadth tapered in the direction of increasin rotation of said shaft; said portions being combined to form a unit, means for angularly adjusting said unit in said solenoid, a separate trapezoidal iron part within said solenoid, means for ang-ularly adjusting said trapezoidal iron part, and an iron repulsion strip circumferentially spaced from said trapezoidal iron part in the direction of increasing rotation of said shaft to produce a crowding of the scale with increasing rotation of said. shaft, said trapezoidal iron and thecircumferential portion of said stationary iron core overlapping one another more or less according to the adjustments of said angular adjusting means.

' 2.-A movable iron. instrument in accordance *with claim 1,.in which each of said angularly adjustingj means. comprises a cyindrical member of' non-magnetizable sheet material rotataby mounted within the opening. of said solenoid, the stationary iron core being secured to one of said members and the trapezoidal iron part being secured totherother of saidmembers.

ALBERT EMANUEL. ANDERSSON.

REFERENCES CITED V The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Date I Name 1,501,189 Record July 15;, 1924 1,560,459 Worrall Nov. 3, 1925 1,600,332 Haslauer Sept. 21, 1926 1,632,623. Rich June 14, 1927 2,183,685 Lingg Dec. 1-939 2,260,026 Hoarez-- Oct. 21,194

FOREIGN PATENTS Number Country Date.

288,665 France May 18, 1899 2,299 Great Britain Dec. 14,1899 

